1. Field of the Invention
This invention is directed to a novel method for making polybenzobisoxazole containing polymers. This is accomplished by first forming a non-polybenzobisoxazole polymer and converting repeat units of the polymer to a polybenzobisoxazole.
2. Description of Related Art
Fibers formed from rod-like polymers are commonly used in a variety of applications including ballistics, ropes and cables, and cut resistant apparel. Polybenzobisoxazole polymers provide excellent physical properties due to their rod-like structure.
Fibers from rod-like polymers are typically formed by extruding a polymer solution through a spinneret. Due to the limited solubility of (cis-polybenzobisoxazole polymers) (c-PBO) such as poly(benzo[1,2 d: 5,4-d′]bisoxazole-2,6-diyl-1,4-phenylene), fibers produced from such polymers are typically spun from strong mineral acids such as polyphosphoric acid (PPA). Residual polyphosphoric acid present in the fiber over time can cause the physical properties of the fiber to degrade.
Also, instead of fibers, polymers such as in the form of films or sheets are likewise useful.
What is therefore needed is a method of producing polymers such as cis isomers of polybenzobisoxazole polymers without the use of polyphosphoric acid.